The USER LIMIT clause specifies the maximum number of global
    buffers each user allocates. Because global buffer pools are
    shared by all users, you must define an upper limit on how many
    global buffers a single user can allocate. This limit prevents a
    user from defining the RDM$BIND_BUFFERS to use all the buffers in
    the global buffer pool. The user limit cannot be greater then the
    total number of global buffers. The default is 5.

    See the Oracle Rdb Guide to Database Performance and Tuning for
    information on determining the maximum number of global buffers a
    user can allocate.

    Although you can change the USER LIMIT IS parameter online, the
    change will only take effect the next time that the database is
    opened. By default, a database can be opened automatically (that
    is, by any user who invokes the database and executes a data
    manipulation language statement). If the database was modified
    so that it must be manually opened, the RMU/OPEN command must be
    used to open it.